Currently, cellular phones are the prevailing means of voice telecommunication. Since mobile phones are frequently used outdoors, for example, ambient noise such as traffic noise often disturbs listening during voice communication. Because of this, output voice clarity enhancement techniques have recently been proposed.
As an output voice clarity enhancement technique, for example, Jpn. Pat. Appln. KOKAI Publication No. 2004-61617 discloses the following technique.
That is, Jpn. Pat. Appln. KOKAI Publication No. 2004-61617 discloses a received voice processing apparatus characterized by comprising a voice frequency analysis unit which calculates a voice spectrum by frequency-analyzing a received voice signal, a target spectrum calculation unit which calculates a target spectrum based on compression ratios for the voice spectrum, which ratios are set for respective frequency bands, a gain calculation unit which calculates, for respective frequency bands, gain values required to amplify the voice spectrum to the target spectrum, a filter coefficient calculation unit which calculates filter coefficients of filter processing for the received voice signal based on the gain values for respective frequency bands, and a filter unit which is set with the filter coefficients and applies filter processing to the received voice signal.
The technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2004-61617 aims at enhancing voice clarity after sound quality deterioration and changes are eliminated without greatly changing the volume of a reproduced voice.
Meanwhile, the opportunity to use content on the Internet (generally called net content) has increased rapidly in recent years. Net content has a wide variety of qualities (source qualities). This is because the quality of net content depends on various factors such as recording environment (creation environment) on the side of content creators, codec parameters upon uploading the net content to servers, and viewing environments (for example, transmission rates and viewing modes) on the side of viewers.
Although the net content has a wide variety of (nonuniform) qualities, since conventional techniques represented by that disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2004-61617 do not assume content having a wide variety of qualities as clarity enhancement processing targets (since they assume only received voices having roughly uniform qualities), various problems are caused.
Emphasis of low-quality sources mostly included in the net content results in further quality deterioration, and excessive correction processing results in an increase in processing volume. Upon execution of clarity enhancement processing, processing is switched depending on changes in ambient noise. However, since processing loads by other applications which run on a system are not taken into consideration, an allowable processing volume of the system is consequently exceeded.
In consideration of these problems and future circumstances of further frequent use opportunities of net content, clarity enhancement processing that assumes playback of content having a wide variety of qualities like net content is demanded.
The present invention has been made in consideration of the above situation, and has as its object to provide a signal correction apparatus which can apply optimal correction processing to content having a wide variety of qualities according to each individual content quality.
According to the present invention, a signal correction apparatus which can apply optimal correction processing to content having a wide variety of qualities according to each individual content quality can be provided.